An electron-beam-pumped light source configured to cause a semiconductor light-emitting device to emit light by emitting an electron beam is expected as a compact light source having high-output ultraviolet rays.
FIG. 12 is an explanatory cross-sectional view illustrating a schematic configuration of an example of an electron-beam-pumped light source of the related art. The electron-beam-pumped light source is configured to emit laser beams, includes a vacuum container 80 hermetically sealed in a state of a negative pressure in the interior thereof and having a light transmitting window 81. In the vacuum container 80, a laser structure 85 including light reflecting members 83, 84 arranged on both surfaces of a semiconductor light-emitting device 82 is arranged on an inner surface of the light transmitting window 81 thereof, and an electron beam source 86 configured to irradiate the semiconductor light-emitting device 82 with an electron beam is arranged on an inner surface of a bottom wall of the vacuum container 80 so as to face the laser structure 85. The semiconductor light-emitting device 82 and the electron beam source 86 are electrically connected to electron accelerating means 87 provided outside of the vacuum container 80 and configured to apply an accelerating voltage. The electron-beam-pumped light source having such the configuration is disclosed in Patent Literature 1.
In the electron-beam-pumped light source described above, electrons emitted from the electron beam source 86 are accelerated by the accelerating voltage applied between the semiconductor light-emitting device 82 and the electron beam source 86 and are formed into an electron beam, light exits from the semiconductor light-emitting device 82 by the electron beam entering the semiconductor light-emitting device 82 via the light reflecting member 84, and the light exits outside as a laser beam through the light transmitting window 81 by being resonated by the light reflecting members 83, 84.
However, in the electron-beam-pumped light source described above, the semiconductor light-emitting device 82 generates heat by being irradiated with the electron beam, and since of the two surfaces of the semiconductor light-emitting device 82 that have a large surface area, one is used as a light-emitting surface and the other surface thereof is used as an electron beam incident surface, the semiconductor light-emitting device 82 is not capable of being cooled from a surface having a large surface area. Hence it is difficult to cool the semiconductor light-emitting device 82 efficiently. Consequently, there are problems that the semiconductor light-emitting device 82 generates heat at a high temperature, whereby luminous efficiency of the semiconductor light-emitting device 82 is lowered and hence high output light is not emitted, and the semiconductor light-emitting device 82 may be broken by heat generation in an early stage.
Also, one means contemplated for obtaining higher light output is increasing the accelerating voltage for the electron beam. However, when the accelerating voltage for the electron beam is increased, there arises a problem that an X-ray is generated from the semiconductor light-emitting device 82.
Also, another means contemplated for obtaining greater light output is increasing a voltage to be applied to the electron beam source 86. However, when the voltage to be applied to the electron beam source 86 is increased, there is a problem that the electron beam source 86 generates heat and breaks in an early stage.
In order to solve the above-described problems, there is proposed an electron-beam-pumped light source configured to cause an electron beam incident on one surface of the semiconductor light-emitting device by an electron gun from a direction oblique thereto so that light exits from the one surface of the semiconductor light-emitting device where the electron beam is incident (see Patent Literature 2). According to the electron-beam-pumped light source, since the semiconductor light-emitting device may be cooled efficiently from a back surface thereof, the semiconductor light-emitting device can be cooled efficiently, and hence a high light output is maintained without lowering the luminous efficiency of the semiconductor light-emitting device.
However, in the electron-beam-pumped light source as described above, since the electron gun is used for irradiating the semiconductor light-emitting device with the electron beam, the one surface of the semiconductor light-emitting device cannot be irradiated with the electron beam uniformly, that is, the one surface of the semiconductor light-emitting device is irradiated with the electron beam locally in an intensive manner, so that there arises a problem that the semiconductor light-emitting device is deteriorated in an early stage.